This invention relates to a clean transfer method and a system therefor, and more particularly to a transfer method which permits components or elements required for the processing and/or assembling of a product associated with a semiconductor to be transferred while being kept clean or free of any contaminant and a system therefor.
A conventional clean transfer method is generally practiced in such a manner as shown in FIGS. 1 and 2. More particularly, a closed space 110 is divided into a maintenance room 112 and a clean room 114 by means of a partition 116. The maintenance room 112 is open to an ambient atmosphere and provided therein with various apparatus 118 used for a precision thin film-forming process required for manufacturing a semiconductor.
The clean room 114 is kept at an air cleanliness ranging from classes 100 to class 10. The words "class 100" used herein indicate a cleanliness having 100 or less particles of 0.5 .mu.m or larger in size contained in one cubic foot of air and the words "class 10" indicate a cleanliness having 10 or less particles of 0.5 .mu.m or larger in size contained in one cubic foot of air. An air stream is blown down from a ceiling of the clean room 114 through a filter 120 into the clean room. The air stream is then outwardly exhausted through a floor 122 formed into a grating construction. In the so-constructed clean room 114 a clean shuttle 124 which is kept at a cleanliness ranging from classes 10 to 1 is movably arranged. The words "class 1" indicate a cleanliness having 1 or less particle of 0.5 .mu.m or larger in size contained in one cubic foot of air. The apparatus 118 are each provided with a transfer port which is open to the surface of the partition facing the clean room 114. A vicinity 126 of each transfer port opening is locally kept at a cleanliness ranging from classes 10 to 1.
The delivery of a transferred object 128 such as a semiconductor wafer or the like between the clean shuttle 124 and the apparatus 118, as shown in FIG. 2, is carried out by introducing the transferred object 128 from the clean shuttle 124 through the vicinity 126 of the periphery of the transfer port locally kept at a cleanliness ranging from classes 10 to 1 to a load lock chamber 130 of the apparatus 118 serving as a preliminary vacuum chamber, closing a shutter of the transfer port on the side of the apparatus to evacuate the preliminary vacuum chamber, and transferring the transferred object 128 to a vacuum chamber 132 of the apparatus 118.
In the conventional clean transfer method shown in FIGS. 1 and 2, the clean room 114 must be kept at a cleanliness as high as classes ranging from 100 to 10 and formed so as to define a large space therein. Unfortunately, much cost is required to keep the clean room 114 at a high cleanliness while maintaining the large space therein. Also, in the conventional clean transfer method, it is required to provide the load lock chamber 130 for receiving the transferred object on the side of the apparatus 118 provided with the vacuum chamber 132, as well as to evacuate the load lock chamber 130 to vacuum. This causes the side of the apparatus to be complicated in structure. In addition, it is substantially impossible to improve the cleanliness to a degree sufficient to render the number of airborne particles substantially near zero. In particular, there is a possibility that particles will contaminate the transferred object during the delivery of the object between the clean shuttle 124 and the apparatus 118.
Another conventional clean transfer method has been proposed and comprises a multi-chamber system as shown in FIG. 3. The multi-chamber system is so constructed that a single load lock chamber provided for accessing a transferred object such as a semiconductor wafer or the like therethrough is commonly used for a sputtering apparatus 134, a CVD apparatus 136, an etching apparatus 138 and the like.
Unfortunately, a clean transfer method using the multi-chamber system shown in FIG. 3 has the following disadvantages: it is impossible to increase the number of apparatus to be arranged in the system, the apparatus cannot be freely arranged, and maintenance is troublesome.
The assignee proposed a clean transfer method as disclosed in Japanese Patent Application Laid-Open Publication No. 28047/1988. However, the publication fails to consider the degree of vacuum in a clean chamber.